It's none other than Jason Momoa, who played Khal Drogo in HBO's "Game of Thrones" and starred in Lionsgate's rebooted Conan the Barbarian!
Most recently, Momoa was seen opposite Sylvester Stallone in the Walter Hill graphic novel adaptation Bullet to the Head.
According to "El Mayimbe," Momoa "flew out to London to screen test on Wednesday" and that he was among a small group that included Isiah Mustafa, Dave Bautista, and Brian Patrick who tested for the role. He continues that "According to sources, Momoa’s screen test went so good that Marvel offered him the part and his reps have now countered, so the negotiations are ongoing."
Because the contract hasn't been signed and there hasn't been an official announcement by Marvel Studios or Disney yet, this casting may change, but this definitely sounds more on par with the kind of scoop we expect to get from the guys at Latino Review.
(Note: According to The Hollywood Reporter's Borys Kitt, no offer has gone out to Momoa as of yet, as he posted on Twitter: "Clarity Alert: My sources are telling me Jason Momoa TESTED for Drax the Destroyer/GUARDIANS OF THE GALAXY but at this time has NO offer.")
Director James Gunn is currently a week into pre-production in London, so we can probably expect more casting news in the coming weeks with Guardians of the Galaxy planned for release on August 1, 2014.